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Linking Dynamic Habitat Selection with Wading Bird Foraging Distributions across Resource Gradients: TFC Model

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posted on 10.05.2015, 16:55 authored by James BeerensJames Beerens

The temporal foraging conditions (TFC) models used daily mean hydrological characteristics calculated throughout the Everglades. Three explanatory variables representing hydrological conditions across a gradient of temporal scales were used as proxies for prey dynamics: days since drydown (DSD) was used as an indicator for long-term prey production (Trexler 2010), recession rate was used as an indicator for prey concentration dynamics (Russell et al. 2002, Beerens et al. 2011), and daily water depth was used as an indicator of short-term prey availability (Gawlik 2002, Beerens et al. 2011). These temporally-specific “resources” were considered available only when cell depths were in the foraging depth range of each species (Beerens et al, in press). The mean levels and heterogeneity (SD) of each resource were used to predict resource selection, which subsequently was used to predict the abundance of flocks and individuals across the landscape. Flock presence was defined as one or more birds of the target species (e.g., egrets, ibises, and storks) detected in a cell, whereas individual abundance counted the total number of birds present. Both individual and flock responses were modeled because wading birds are highly social and select foraging habitat based in part on the presence of conspecifics, a process that may increase or decrease individual fitness (Campomizzi et al. 2008). For the TFC, daily output summed over each region (Water Conservation Area (WCA) 1, WCA-2, WCA-3N, WCA-3S, Big Cypress National Park (BCNP), and Everglades National Park (ENP); Fig. 1) represents the mean patch quality of the landscape, within the suitable water depths of each species.


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